This project is intended to clarify the mechanisms of exercise intolerance in patients with heart failure, chronic obstructive lung disease and in healthy sedentary elderly persons. The specific objective is to determine whether the exercise intolerance is due to inactivity, or if these chronic diseases cause an impairment in muscle oxygen utilization. The specific aims are threefold: 1) To determine if exercise training rehabilitates skeletal muscle function in patients with heart failure and lung disease, independent of muscle blood flow and arterial oxygenation, to equal the muscle function of age-matched normals, 2) to determine if induced heart failure in pigs impairs skeletal muscle function beyond that produced by physical inactivity, and 3) to determine if systemic factors, such as tumor necrosis factor, released in some chronic diseases cause muscle dysfunction, and reduce the muscle's ability to use oxygen. This project will extend the knowledge of exercise intolerance in patients with chronic diseases.